1. Field of the Invention
The present invention relates to an arm with an attachment removable unit capable of easily removing an attachment from an arm of a construction equipment and, more particularly, relates to an arm with an attachment removable unit capable of easily removing an attachment from an arm while maintaining the performance of a front portion such as a hydraulic shovel or excavator, a tractor shovel, or the like.
2. Description of the Related Art
In general, a construction equipment, for example, a hydraulic shovel, a tractor shovel, or the like, is provided at its main body of a work vehicle with at least an arm as a member forming a front portion thereof and also provided at the tip portion of the arm with a bucket, for example, as an attachment so as to be operable for various works. The attachment is exchanged for a new one such as a normal excavating bucket, a bucket with a wide width, a bucket for forming a normal plane, a breaker for breaking the road surface or a rock, a ripper, or the like, in accordance with the kind, contents or state of the work. In the case of performing such an exchanging operation of an attachment, it is necessary to align the hole for a pin at the tip portion of the arm with the hole for a pin of the attachment and then draw or insert the pin, so that at least two workers are required. Since much time and many workers are required for such an exchanging operation of the attachment, there has been proposed an attachment removable unit for performing the attachment exchanging operation efficiently. There is a technique (hereinafter called a prior art) disclosed in JP-A-6-264466 as an example of such a kind of conventional attachment removable unit.
An attachment removable unit 101 according to such a prior art includes as shown in FIGS. 7 and 8 a main frame 9 having at one of its opposite ends a boss 15 into which a coupling pin 19 at the tip end side of an arm 1 is pressed and also having at the other of the opposite ends a boss 16 into which a pin 21 for coupling a link 3 is pressed. The attachment removable unit 101 further includes a first hook 6 for engaging with one coupling pin (hereinafter called a first pin) 18 of a bucket 2 and a second hook 7 for engaging with the other coupling pin (hereinafter called a second pin) 17 of the bucket 2. The bosses 15, 16 and the first and second hooks 6, 7 are disposed in a manner that a line a1-a2 connecting the center portions of the bosses 15, 16 is substantially in parallel to a line b1-b2 connecting the first and second hooks 6, 7 with a distance L therebetween. Further, a hydraulic cylinder 20 is provided in order to adjust the distance between the first pin 18 and the second pin 17.
The attachment removable unit 101 according to the thus arranged prior art is attached to an arm 1' in a manner that a pair of the main frames 9 are disposed so as to sandwich the arm 1' shown in FIG. 6 therebetween from the outside of the opposite side walls of the arm 1', then the pin 19 for coupling the arm 1' is pressed into the boss 15, and the pin 21 for coupling the link 3 is pressed into the boss 16.
In this state, the bucket 2 serving as an attachment is attached to the arm in a manner that the second hook 7 is hung at the second pin 17 on the bucket 2 side and the first hook 6 is hung at the first pin 18 on the bucket 2 side, and then these pins are engaged with the hooks by applying a predetermined pressing force by means of the hydraulic cylinder 20.
Accordingly, according to the prior art, since the attachment can be easily exchanged, the aforesaid problem relating to the time and workers for the attachment exchanging operation can be eliminated.
Although the above-described prior art is able to obviate the conventional problem relating to the time and workers for the attachment exchanging operation in this manner, there arises the following new problem in the aforesaid prior art due to the structure of the attachment removable unit and the structure of the arm.
That is, in the aforesaid prior art, the distance from the rotation fulcrum (the center portion of the coupling pin 19) on the arm 1' side to the tip end of the bucket 2 becomes longer by the distance L between the aforesaid line a1-a2 and the line b1-b2, so that the rotation range of the bucket 2 becomes longer as compared with the case where the attachment removable unit 101 is not provided. Thus, in the state where an attachment hydraulic cylinder 5 is fully extended, the tip portion of the bucket 2 may contact with the lower plate of the arm 1', or, although not shown, the tip portion of the bucket 2 may interfere with the main body of the hydraulic shovel depending on the posture of the boom and the arm 1' of the hydraulic shovel, for example. Further, since the maximum driving force of the attachment hydraulic cylinder 5 is a predetermined value irrespective of the presence or not-presence of the attachment removable unit 101, the excavation force decreases by an amount corresponding to the increased distance of the rotation distance from the rotation fulcrum to the tip end of the bucket 2 due to the presence of the attachment removable unit.